Javascript TypeError:无法读取属性'；接收方id'；未定义的

此功能是在有人向用户发送请求时向用户发出通知 我正在为learning purposs创建一个消息应用程序，但无法解决此问题。firebase控制台不断给出错误：firebase函数

TypeError: Cannot read property 'receiver_id' of undefined
   at exports.sendNotification.functions.database.ref.onWrite.event 
(/user_code/index.js:9:36)
at Object.<anonymous> (/user_code/node_modules/firebase-functions/lib/cloud- 
   functions.js:112:27)
    at next (native)
at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:28:71
at __awaiter (/user_code/node_modules/firebase-functions/lib/cloud- 
   functions.js:24:12)
at cloudFunction (/user_code/node_modules/firebase-functions/lib/cloud- 
   functions.js:82:36)
at /var/tmp/worker/worker.js:728:24
    at process._tickDomainCallback (internal/process/next_tick.js:135:7)

---

params

由

onWrite

回调函数的函数提供

.onWrite((snapshot, context) => {
  const receiver_id = context.params.receiver_id;
});

---

您在

onWrite

中的

事件

中有什么内容？错误消息告诉您，

event.params.received_id

中未定义

params

，现在它返回另一个错误

TypeError:无法读取exports.sendNotification.functions.database.ref.onWrite中未定义的属性“val”

.onWrite((snapshot, context) => {
  const receiver_id = context.params.receiver_id;
});